Abstract
During a search for glycosidase inhibitors among marine natural products, we applied an integrated in vitro and in silico approach to evaluate the potency of some aaptamines and makaluvamines isolated from marine sponges on the hydrolyzing activity of α-N-acetylgalactosaminidase (α-NaGalase) from human cancer cells and the recombinant α-D-galactosidase (α-PsGal) from a marine bacterium Pseudoalteromonas sp. KMM 701. These alkaloids showed no direct inhibitory effect on the cancer α-NaGalase; but isoaaptamine (2), 9-demethylaaptamine (3), damirone B (6), and makaluvamine H (7) reduced the expression of the enzyme in the human colorectal adenocarcinoma cell line DLD-1 at 5 μM. Isoaaptamine (2), 9-demethylaaptamine (3), makaluvamine G (6), and zyzzyanone A (7) are slow-binding irreversible inhibitors of the bacterial α-PsGal with the inactivation rate constants (kinact) 0.12 min−1, 0.092 min−1, 0.079 min−1, and 0.037 min−1, as well as equilibrium inhibition constants (Ki) 2.70 µM, 300 µM, 411 µM, and 105 µM, respectively. Docking analysis revealed that these alkaloids bind in a pocket close to the catalytic amino acid residues Asp451 and Asp516 and form complexes, due to π-π interactions with the Trp308 residue and hydrogen bonds with the Lys449 residue. None of the studied alkaloids formed complexes with the active site of the human α-NaGalase.
Highlights
Marine organisms, in particular marine sponges, are inexhaustible source of metabolites with various biological activities
Roswell Park Memorial Institute Medium (RPMI 1640), phosphate buffered saline (PBS), L-glutamine, penicillin-streptomycin solution, trypsine and fetal bovine serum (FBS), sodium hydrocarbonate (NaHCO3 ), and agar were purchased from BioloT (Bolshoy Sampsonievsky avenue, Saint-Petersburg, Russia), p-nitrophenyl-N-acetyl-α-D-galactosaminide (p-NPNA-α-Gal), p-nitrophenyl-α-D-galactopyranoside, and Bradford reagent were purchased from Sigma-Aldrich
Alkaloids were reisolated from repository samples of marine sponges Aaptos aaptos and Zyzzya fuliginosa
Summary
In particular marine sponges, are inexhaustible source of metabolites with various biological activities. A large group of secondary metabolites isolated from marine sponges are alkaloids [1]. Marine sponges of the genera Latrunculia, Batzella, Prianos, Zyzzya are a rich source of alkaloids bearing a pyrrolo[4,3,2-de]quinoline skeleton [2]. Pyrroloquinoline alkaloids have shown a variety of biological activities, including antifungal and antimicrobial [3], antioxidant [4], antimalarial activity [5]; inhibition of the HIF-1α/p300 interaction [6]. It is shown that numerous pyrroloiminoquinone alkaloids, including synthetic analogues, are active, their mechanisms of action, pharmacological properties, and safety have shown that they have great potential for creating new anticancer drugs [10]
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